What type of lens has two curves on its front surface?

The type of lens that has two curves on its front surface is the plus cylinder lens. This lens is specifically designed with a convex front surface that has different curvature in two perpendicular meridians. The unique shape allows the lens to correct astigmatism by focusing light differently along these axes, thereby allowing the wearer to see clearly at specific angles.

The distinction of being called a "plus cylinder lens" comes from its ability to provide positive (convex) power in one meridian while being flat or having no power in the perpendicular axis. Understanding the geometry of the plus cylinder lens is essential for addressing various refractive errors, particularly in patients with astigmatism.

Bifocal and trifocal lenses, while they do have multiple focal points, consist of separate distinct areas designed for different vision needs rather than having two curves on a single surface. Concave lenses typically have a single inwardly curved surface designed to diverge light rays, making them distinct as well. This context highlights why the plus cylinder lens is the correct answer for this question.